As the most important rock-breaking tool in the drilling engineering, cone bits play a leading role in the downhole rock-breaking operation, and their working performance directly influences the drilling quality, the drilling efficiency and the drilling cost. The service life of the cone bits almost directly depends on the service life of the bit bearings, and in turn, the service life of the bit bearings depends on the seal life. The recent development trend of cone bits is to realize their high speed. With the continuous increase in the rotation speed of bits, the weakness of common bearing seals used in the rough environment is increasingly prominent. Therefore, during the researches on bits, the improvements of the service life of bearings cannot be ignored. As the weakest link of a high-speed cone bit and a quick-wear component, a bearing seal is the most critical factor that determines the service life of the high-speed cone bit. A statistical analysis of field data has indicated that the failed bits caused by the early damage to bearings account for 80% of the total number of failed bits, and the bearings seriously worn due to the early failure of seals account for 30% of the total number of failed bearings. The bearing seal problem of the cone bits has become a technical bottleneck that seriously influences the drilling efficiency and drilling cost of high-speed cone bits, and has become a problem to be urgently solved in the oil drilling and production engineering at present.
The practices have indicated that the sealing performance of the current conventional cone bit bearings cannot meet the operation requirements very well; and particularly during drilling at a high rotation speed, the seals reveal short service life, poor durability, and serious wear and aging. The working conditions for seals of the cone bits are very severe, including high temperature, high-abrasiveness medium, high loads and very small sealed cavity. These working conditions and environments aggravate the failure of seals, and bring tremendous difficulties and challenges to the researches on seals. The entrance of the abrasive medium slurry is the most critical factor that influences the service life of seals for high-speed cone bits. The existing bearing seals belong to passive seals which have no automatic sand draining function, so that the seals will be quickly worn and thus failed once slurry particles enter the sealed cavity. At present, there are still no testing devices for a spiral seal of a high-speed cone bit. The experimental researches are the premise and guarantee for smoothly conducting field tests and product applications, and the testing devices are the key to determine whether the experimental researches are successful. The development of testing devices for a spiral seal of a high-speed cone bit is very important to improve the service life of bits.
Therefore, how to change the current situation in the prior art that it is unable to conduct tests on a spiral seal of a high-speed cone bit is a problem to be urgently solved by those skilled in the art.